Algebra II : Algebra II

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #3 : Polynomials

Factor the following trinomial: \displaystyle 7x^{2} - 11x -6.

Possible Answers:

\displaystyle (x + 3)(7x - 2)

\displaystyle (7x + 2)(x - 3)

None of these answer choices are correct.

\displaystyle (7x + 3)(x - 2)

\displaystyle (5x^{2} - 4x - 2)(2x^{2} - 7x - 4)

Correct answer:

\displaystyle (7x + 3)(x - 2)

Explanation:

To factor trinomials like this one, we need to do a reverse FOIL. In other words, we need to find two binomials that multiply together to yield \displaystyle 7x^{2} - 11x - 6.

Finding the "first" terms is relatively easy; they need to multiply together to give us \displaystyle 7x^{2}, and since \displaystyle 7 only has two factors, we know the terms must be \displaystyle 7x and \displaystyle x. We now have \displaystyle (7x    \displaystyle )(x    \displaystyle ), and this is where it gets tricky.

The second terms must multiply together to give us \displaystyle -6, and they must also multiply with the first terms to give us a total result of \displaystyle -11x. Many terms fit the first criterion. \displaystyle (-2)(3), \displaystyle (-3)(2), \displaystyle (-6)(1) and \displaystyle (-1)(6) all multiply to yield \displaystyle -6. But the only way to also get the "\displaystyle x" terms to sum to \displaystyle -11x is to use \displaystyle (7x + 3)(x - 2). It's just like a puzzle!

Example Question #2 : How To Factor A Variable

Factor the expression:

\displaystyle \small x^2y^3z^2+x^4y^3z

Possible Answers:

\displaystyle \small x^2y^3z^2+x^4y^3z

\displaystyle \small xyz(xy^2+x^3y^2)

\displaystyle \small x^2y^3z(z+x^2)

\displaystyle \small x^2(y^3z^2+x^2y^3z)

\displaystyle \small (x^2y^3z^2)(x^4y^3z)

Correct answer:

\displaystyle \small x^2y^3z(z+x^2)

Explanation:

To find the greatest common factor, we must break each term into its prime factors:

\displaystyle \small x^2y^3z^2 = x \cdot x \cdot y \cdot y \cdot y \cdot z \cdot z

\displaystyle \small x^4y^3z= x \cdot x \cdot x \cdot x \cdot y \cdot y \cdot y \cdot z

The terms have \displaystyle \small x^2\displaystyle \small y^3, and \displaystyle \small z in common; thus, the GCF is \displaystyle \small x^2y^3z.

Pull this out of the expression to find the answer: \displaystyle \small x^2y^3z(z+x^2)

Example Question #4 : Variables

Factor the trinomial.

\displaystyle 6x^{2}-31x+35

Possible Answers:

\displaystyle (3x-7)(2x+5)

\displaystyle (3x-7)(2x-5)

\displaystyle (2x+7)(3x-5)

\displaystyle (2x-7)(3x-5)

\displaystyle (2x-7)(3x+5)

Correct answer:

\displaystyle (2x-7)(3x-5)

Explanation:

Use the \displaystyle ac-method to split the middle term into the sum of two terms whose coefficients have sum \displaystyle -31 and product \displaystyle 6*35 = 210. These two numbers can be found, using trial and error, to be \displaystyle -21 and \displaystyle -10.

\displaystyle -21*-10=210 and \displaystyle -21+(-10)=-31

Now we know that \displaystyle 6x^{2}-31x+35 is equal to \displaystyle 6x^{2}-10x-21x+35.

Factor by grouping.

\displaystyle (6x^{2}-10x)-(21x-35)

\displaystyle 2x(3x-5)-7(3x-5)

\displaystyle (2x-7)(3x-5)

Example Question #1 : Variables

Factor completely: \displaystyle 3x^{2} - 45x - 96

Possible Answers:

\displaystyle (3x-16)(x+2)

\displaystyle 3(x^{2} - 15x - 32)

\displaystyle 3 (x-16)(x+2)

The polynomial cannot be factored further.

\displaystyle 3 (x-8)(x+4)

Correct answer:

\displaystyle 3(x^{2} - 15x - 32)

Explanation:

First, we note that the coefficients have an LCD of 3, so we can factor that out:

\displaystyle 3(x^{2} - 15x - 32)

We try to factor further by factoring quadratic trinomial \displaystyle x^{2} - 15x - 32. We are looking to factor it into two factors\displaystyle (x+ ? )(x+?), where the question marks are to be replaced by two integers whose product is \displaystyle -32 and whose sum is \displaystyle -15

We need to look at the factor pairs of \displaystyle -32 in which the negative number has the greater absolute value, and see which one has sum \displaystyle -15:

\displaystyle \begin{matrix} \textrm{Pair} & \textrm{Sum} \\ 1,-32& -31\\ 2,-16&-14 \\ 4,-8& -4 \end{matrix}

None of these pairs have the desired sum, so \displaystyle x^{2} - 15x - 32 is prime. \displaystyle 3(x^{2} - 15x - 32) is the complete factorization.

Example Question #2 : Factoring Polynomials

Simplify:

\displaystyle \frac{4x-2}{2-4x}

Possible Answers:

\displaystyle 1

\displaystyle x-2

\displaystyle 0

\displaystyle -1

\displaystyle x

Correct answer:

\displaystyle -1

Explanation:

When working with a rational expression, you want to first put your monomials in standard format.

Re-order the bottom expression, so it is now reads \displaystyle -4x+2

Then factor a \displaystyle -1 out of the expression, giving you \displaystyle -1(4x-2).

 The new fraction is  \displaystyle \frac{4x-2}{-1(4x-2)}.

Divide out the like term, \displaystyle (4x-2), leaving \displaystyle \frac{1}{-1}, or \displaystyle -1.

Example Question #1 : Equations / Solution Sets

Factor \displaystyle 3u^4 - 24uv^3.

 

Possible Answers:

\displaystyle 3u(u^3 - 8v^3)

\displaystyle 3u(u - 2v)(u + 2v)

\displaystyle 3u(u - 2v)(u^2 - 2uv -4v^2)

\displaystyle 3u(u - 2v)(u^2 + 2uv + 4v^2)

\displaystyle 3u[u^3 - (2v)^3]

Correct answer:

\displaystyle 3u(u - 2v)(u^2 + 2uv + 4v^2)

Explanation:

First pull out 3u from both terms.

3u4 – 24uv= 3u(u3 – 8v3) = 3u[u3 – (2v)3]

This is a difference of cubes. You will see this type of factoring if you get to the challenging questions on the GRE. They can be a pain to remember, but pat yourself on the back for getting to such hard questions! The difference of cubes formula is a3 – b3 = (a – b)(a2 + ab + b2). In our problem, a = u and b = 2v:

3u4 – 24uv= 3u(u3 – 8v3) = 3u[u3 – (2v)3]

                = 3u(u – 2v)(u2 + 2uv + 4v2)

Example Question #2 : Equations / Solution Sets

Factor \displaystyle 36x^2 - 49y^2.

Possible Answers:

Cannot be factored any further.

\displaystyle (6x + 7y)(6x -7y)

\displaystyle (6x + 7y)(6x + 7y)

\displaystyle 6x^2 - 7y^2

\displaystyle (6x - 7y)(6x - 7y)

Correct answer:

\displaystyle (6x + 7y)(6x -7y)

Explanation:

This is a difference of squares. The difference of squares formula is a2 – b2 = (a + b)(a – b).

In this problem, a = 6x and b = 7y:

36x2 – 49y= (6x + 7y)(6x – 7y)

Example Question #1191 : Algebra Ii

Factor:

\displaystyle 2x^{2}-7x+6

Possible Answers:

\displaystyle (x+2)(2x+3)

\displaystyle (x+1)(2x+6)

\displaystyle (x-2)(2x-3)

\displaystyle (x-1)(2x-6)

\displaystyle (2x-2)(x-3)

Correct answer:

\displaystyle (x-2)(2x-3)

Explanation:

\displaystyle 2x^{2}-7x+6

\displaystyle =2x^{2}-3x-4x+6

\displaystyle =2x^{2}-3x-(4x-6)

\displaystyle =x(2x-3)-2(2x-3)

\displaystyle =(x-2)(2x-3)

Example Question #13 : Factoring Polynomials

Factor the following expression:

\displaystyle x^2 -10x - 24

Possible Answers:

\displaystyle (x-12)(x-2)

\displaystyle (x-6)(x+4)

\displaystyle (x+3)(x-8)

\displaystyle (x-12)(x+2)

\displaystyle (x-24)(x-1)

Correct answer:

\displaystyle (x-12)(x+2)

Explanation:

\displaystyle x^2 -10x - 24

To factor, we are looking for two terms that multiply to give \displaystyle -24 and add together to get \displaystyle -10.

Possible factors of \displaystyle -24:

\displaystyle (-1,24),\ (1,-24),\ (-2,12),\ (2,-12),\ (-3,8),\ (3,-8),\ (-4,6),\ (4,-6)

Based on these options, it is clear our factors are \displaystyle 2 and \displaystyle -12.

\displaystyle (2)(-12)=-24\ \text{and}\ 2+(-12)=-10

Our final answer will be:

\displaystyle (x-12)(x+2)

Example Question #61 : Polynomials

Factor the following expression:

\displaystyle x^2 +7x - 8

Possible Answers:

\displaystyle (x-8)(x+1)

\displaystyle (x-4)(x-2)

\displaystyle (x+4)(x-4)

\displaystyle (x+4)(x-2)

\displaystyle (x+8)(x-1)

Correct answer:

\displaystyle (x+8)(x-1)

Explanation:

\displaystyle x^2 +7x - 8

To factor, we are looking for two terms that multiply to give \displaystyle -8 and add together to get \displaystyle 7.

Possible factors of \displaystyle -8:

\displaystyle (-1,8),\ (1,-8),\ (-2,4),\ (2,-4)

Based on these options, it is clear our factors are \displaystyle -1 and \displaystyle 8.

\displaystyle (-1)(8)=-8\ \text{and}\ (-1)+8=7

Our final answer will be:

\displaystyle (x+8)(x-1)

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